Information industry has become one of the most important industries in the world. To maintain the superiority in this competitive field, increasing the efficiency in producing computers is necessary. In the past, the processes of securing a mother board on the baseplate in assembling computers are as shown in FIGS. 1 and 2. FIG. 1 shows a bolt. While assembling a mother board onto the baseplate, the bolt is first screwed into a threaded hole preset on the baseplate, and then a screw is inserted through a threaded hole on the mother board and screwed into the bolt secured on the baseplate, so as to fix the mother board on the baseplate. In this manner, two screwing operations are required and threaded holes must be prepared in advance on the baseplate, which manner takes much time. FIG. 2 shows a holder having a top face and four vertical sidewalls. The top face is formed thereon with a threaded hole or provided with a hook. On both sides of the middle of each vertical sidewall are provided with projections and on the end of each vertical sidewall is formed with a horizontal flange with a gap formed between the horizontal flange and one end of the projection, the gap being the same thickness as that of the baseplate. While assembling a mother board, the holder is first inserted from the back of the baseplate (opposite to the side of the mother board) into a rectangular hole preformed on the baseplate and then secured on the baseplate through the gaps between the horizontal flanges on the ends of the vertical sidewalls and the ends of the projections. Further, a screw is inserted through the threaded hole on the mother board and screwed into the threaded hole on the top face of the holder secured on the baseplate, or the hook on the top face of the holder can hook an edge of the mother board so as to secure the mother board on the baseplate. With such a holder, although the operations of screwing can be eliminated and thus the time for assembling is decreased, such a holder is not easy to manufacture and requires more material, which results in increased production cost. In addition, during assembling, the baseplate has to be turned over so as to allow the holder to be inserted into the baseplate from the back thereof and fixed thereto and the baseplate has to be turned over further for attaching the mother board thereon, which causes the inconvenience in assembling and extends the time of assembly. Further, in case the hook on the top face of the holder was found misguided, the baseplate has to be turned over again to release and reinstall the holder, which seriously delays the process of assembly.